A Novel Charging Control for D-EPC with DC Power Sources Connected in Series

Abstract

A new multiple DC-inputs direct electric-power converter (D-EPC) was proposed. It can be applied to motor-drive systems with two direct-current (DC) power sources. The D-EPC can charge a DC power source with motoring by another DC power source. This charging is controlled by the voltage command multiplied by a power distribution ratio of more than 1.0 for the DC power source supplying power to the motor and another DC power source. If charging power is required in the condition of phase voltage saturation, the phase voltage command calculated using the power distribution ratio of more than 1.0 cannot be increased to more than the phase voltage limit. This paper proposes a new charging control for D-EPCs by controlling the switches on the free-wheel current path. The distribution ratio of this proposed control does not exceed 1.0. The simulation results showed that one DC power source can be charged with motoring by another DC power source using the proposed charging control.

Experimental verification of voltage boost control in a hybrid system using D‐EPC

“…The offsets can be set arbitrarily as long as Equation ( 10) is met; in this study, the values of m oa , m ob were calculated based on the time distribution in PWM cycle (corresponding to the power distribution ratio) and voltage error compensation. [11][12][13][14] The time distribution ratio ρ a corresponding to the power distribution ratio of source a is as shown in Equation (11). (11) The offset m oa for the modulation rate of source a is derived as shown in Equation (12).…”

“…[11][12][13][14] The time distribution ratio ρ a corresponding to the power distribution ratio of source a is as shown in Equation (11). (11) The offset m oa for the modulation rate of source a is derived as shown in Equation (12). The standard offset is set to the upper limit of triangular wave, that is 1, and treated as an absolute value because the time distribution ratio is always positive.…”

“…In power distribution control of D-EPC, the motor's dq-axis current command is converted to a three-phase voltage command using vector control; after that, the voltage command is multiplied by a power distribution ratio to calculate the phase voltage command for each power source. [10][11][12][13][14] In addition, to generate PWM signals by triangular wave comparison, a modulation rate is calculated to normalize the phase voltage references of each power source by triangular wave amplitude. Derivation of the modulation rate m ua for u-phase of source a is shown in Equation ( 1).…”

“…However, D‐EPC actuates inverter circuits connected to respective power sources within a carrier cycle by using phase voltage commands that can be easily calculated by multiplying by a power distribution ratio. This power distribution control in D‐EPC makes possible DC power distribution in each carrier cycle, thus featuring high control responsiveness, which differentiates D‐EPC from neutral‐point potential control in three‐level inverters 10–14 …”

“…This power distribution control in D-EPC makes possible DC power distribution in each carrier cycle, thus featuring high control responsiveness, which differentiates D-EPC from neutral-point potential control in three-level inverters. [10][11][12][13][14] This paper proposes a hybrid system in which one of the D-EPC power inputs is a smoothing capacitor for voltage boost, and two D-EPC circuits are used for the drive motor and the generators, respectively. Besides, power distribution control is applied to power produced by the generator so as to control the capacitor boost.…”